The invention concerns instruments for carrying out an operating procedure on the joint of a patient, in particular a finger joint. In addition the invention concerns an operating method of replacing a joint of a patient, in particular a finger joint, preferably a finger middle joint.
In any gripping function by the hand the middle joint (the PIP joint) of the finger implements almost the greatest and most important part of the bending power of the finger and is therefore indispensable in its ability to operate for the essential forms of gripping action by the hand (gripping items forcibly, gripping large items, gripping keys gripping combs, gripping writing implements and so forth). If the function of the PIP joint is reduced due to pain and/or a restriction on movement ultimately the overall function of the hand also suffers. Pain cannot be permanently treated with medication as medications loose their effectiveness and often cause undesired incompatibilities and have side-effects.
External immobilisation is extremely impracticable and uncomfortable in everyday life, and in addition the function of the finger is markedly impeded. That ultimately applies also to ‘internal’ immobilisation of the injured joint, which immobilisation was and still is implemented in the form of a functionally appropriate or individually desired position by means of what is referred to as arthrodesis of the PIP joint, that is to say bone fusion of the middle and base joint. Freedom from pain can in that way actually always be achieved, but the stiffening of the joint is actually not acceptable having regard to the above-outlined enormous importance of the PIP joint in terms of the overall functioning of the hand. In that respect it is in principle to be considered that increasingly also and in particular older people are reliant on proper operability of their hands as many cannot manage for themselves and their own wish for independence and the necessity for independence are continually on the rise.
Many different endeavours have been made over many years to arrive at suitable solutions for joint replacement on the fingers. Hitherto however it has not yet been possible for any design to prove crucially successful as none adequately complies with all important target criteria.
Implants used at the present time suffer from certain disadvantages and do not meet the target criteria.
On the one hand Swanson Silastic spacers are used, which in spite of the induction of foreign body granuloma, the risk of material fracture and guidance instability, often give astonishing results, in particular in relation to rheumatoid arthritis. Those movable spacers which actually do not represent a joint have therefore certainly a firm place in relation to this indication. The limit of what is viable however is rapidly reached therewith, with a high level of substance loss and advanced destruction.
Present coupled ‘genuine’ joint implants such as for example the St. George endoprosthesis are inserted dorsally and cemented in place, but frequently exhibit loosening effects and often involve a poor function, which is to be attributed to the high tensile and frictional forces, for which reason that method is inadequate.
Nowadays the idea of surface replacement with reconstruction of the utmost accuracy of the predetermined anatomy is favoured, and non-coupled implants in the form of the pyrocarbon endoprosthesis and the moje ceramic implant are the leading representatives. As anatomically the middle joint is also not a pure hinge joint but involves a rotational-sliding movement, the endeavour is ultimately the most natural motion without potentially harmful tensile and rotational forces. The previous operational observations and investigations however could not demonstrate that as a rule the endoprostheses involve bony integration, on the contrary they rather do not grow into place, and exhibit migration and bone extension phenomena which prevent a good functional result.
In addition those endoprostheses have to be fitted by a stretching apparatus, which precisely signifies injury to that enormously sensitive functional structure, with the consequences of limited early functionality, fibroses and deformations which possibly necessitate further interventions for releasing the joint, as well as shrinkage phenomena which sometimes result in stretching contraction. The attempt to implant the endoprosthesis by way of the flexural side is intended to represent an alternative, but here crucially sensitive tissue is also injured, which can limit the function due to healing effects.
The partially necessary removal of such joints then also impressively shows that, due to the respective prosthesis shank, bone substance has scarcely remained besides the cortical ‘sheath’ of the phalanges, a hollow tube which requires a great deal of sound bone substance for an arthrodesis which is then necessary.
The indications in respect of such implants arise out of the described facts: lack of early mobilisation mean that contracted, pre-operated joints with tendon deformation and adhesions appear inappropriate, and equally joint instabilities are not a suitable condition.
Long years of surgical activity on hands mean that the critical operator is always discontent with the fact that the motor functional structures on the fingers, the extension and flexing tendons in their complexity and the sensitivity linked thereto, in spite of the most careful treatment, always leave behind healing symptoms with the environment, which often crucially limit the finger function. Secondary tendon dissolutions are linked to extreme risks and can often leave behind results which are equally poor as previously. If exercise is taken too early after a tendon suture the tissue possibly does not stick together but then there is a functional limitation due to suture insufficiency. It would be best for those structures not to be surgically treated at all if that does not have to be done.
In addition in the case of a disturbance to a finger function finger reconstruction by joint replacement should not be ruined by sound tissue being damaged in the course of the operation.